GNCLONE

Have not raced it yet, but is seems to move along nicely.

ZONES89RS

iTrader: (25)

Nice rise, makes the monte carlo look bad, LOL.

GNCLONE

Seems to hook up pretty well. Zone, you guys with F bodies have that better rear end setup with the torque arm and the panhard rod etc.

ZONES89RS

iTrader: (25)

It is cheap, i know that much, but the TQ arm does not make dual exhaust easy.

speedtigger

iTrader: (16)

I owned and raced a couple GNs for years. How does the driving experience compare to the old turbo engine?

GNCLONE

I remember you (Tigger) posted a youtube video a few months ago of your GN.

This thing feels like a GN because I've got a bad bog when I floorboard the gas pedal. Then it slowly spools up and it is gone. Like a turbo. A friend suggested I replace the vac secondary spring but I can't remember if he said the stiffer one or the softer one.

It is a 670 Holley dual feed, I have a regulator, a return and about 6-7 psi.

speedtigger

iTrader: (16)

Do I know you from the racetrack?

On the vac secondary spring, it is stiffer to eliminate a bog. If that doesn't do it, it may be a lean bog. If so going up a couple main jet sizes should take care of it.

hifi875

iTrader: (2)

try a 50cc accell pump before you do the spring thing. they come with a 30cc. not enough if you are usinga vic. jr. i had the same problem with my setup and that fixed it. i am running a 670 avenger vac sec. carb.

GNCLONE

I am not new to building cars, but I am new to carburetors. Thanks for the advice.

Hifi - you and I might have the exact same setup.

TXoldskool

iTrader: (1)

congrats on getting it "done"! Tho....they never are really finished are they?

On the bog....my 6.0 had the same issue...needed bigger squirters primary and secondary and primary pump cam. I have a larger Holley 750 HP Street...so your 670 surely needs a bigger pump shot? I haven't upgraded to a 50cc pump yet...but running .40 squirter front and I think a .37 rear now (and it might even like .42 or .45 on the primary and .40 secondary?) its in my future. Truck has not been fine tuned yet on a dyno or at the track. Damn heat keeping me away from the track but gave me time to order new rear rubber (M/T ET d/r's) tho... so hopefully soon it will be able hook up. Even with relocating the fuel tank from the cab to behind the 12 bolt 3.73 posi rear axle...on the street now it'll spin both 275/60-15 BFG's in 1st at any speed... and half way thru 2nd. That wouldn't get me good ET's at the track!

GNCLONE

Thanks.

Mine won't spin the tires unless I hold it with the brakes. It has drag radials so that might be part of the reason, 3.23s might be the other reason.

I definitely need to do some work on the carb, but if I "ease" into the secondaries slowly there is no bog.

TXoldskool

iTrader: (1)

your carb is looking for more fuel during the "transition" phase. When you push the accelerator your carb needs a shot of gas....and if it breath's well...a big shot of gas. Your 6.0L is looking for more fuel then your carb is currently giving it. Have you done a plug check? Or... do you have a/f gauges? They help a lot. I could see it go lean with throttle tip in....so I compensated with bigger squirters/cams and the lean bog is gone.
I just need to dial in idle and cruise better.....its too rich.


Some reading for you. Next thing you know...you'll be tuning like a pro.
chevyhardcore.com/tech-stories/engine/modern-tuning-techniques-for-holley-carburetors/

improving-mileage-performance-and-drivability-on-carbureted-cars/

TXoldskool

iTrader: (1)

wooops.........................dbl post.

GNCLONE

I'm not a noob! I feel like one though. I have built two 5.0 Mustangs from the ground up but they were both EFI.

A 670 Street Avenger is a single pumper - that means accelerator pump, right? Squirter is slang for accelerator pump? A single pumper has two squirters and one cam? A double pumper has four squirters and two cams?

speedtigger

iTrader: (16)

Yep. "double pumper" is the same thing as a mechanically operated secondary carburetor. So, you will hear people say double pumper or mechanical secondaries when referring to Holley style carbureters. While vacuum secondaries or "single pump" as you referred to it would be the same.

A general rule of thumb is that cars with manual transmissions or high stall torque converters almost always run faster and are more fun to drive with a mechanical secondary carburetor. Vacuum secondary carburetors shine in cars with factory low stall torque converters and/or low numerical rear gear ratios like 3.36 or lower. Also, if a main concern is fuel economy, the vacuum secondary carbs have inherent advantages.

TXoldskool

iTrader: (1)

Wasn't trying to offend as I know you're no green kid.....I only provided links to carb info!

The accelerator pump and the pump cam are related to the squirter yes. And a "double pumper" has 2 accelerator pumps, both a primary and a secondary each with a squirter, and each squirter has 2 holes...one for each barrel.

As for your carb...other then the spring...looks like the power valve and main jets are all else that can be changed for the secondaries. Maybe try a higher power valve number?

GNCLONE

Thanks tigger, and thanks TX - no offense taken. I appreciate the help.

One more Q:

I'm getting TERRIBLE mileage right now (10 mpg?) but it doesn't seem to be running rich. I can tell rich by smell and a black sooty tailpipe, I don't have either. Could it be lean but burning fuel b/c I don't have my lockup function wired on the convertor?